Introduction to the International System of Units (SI) and the Metric System

1. Introduction to the International System of Units (SI) and the Metric System Mr. Tang and Mr. Pulickeel SPH3U1 September 2008

2. In the beginning • Back in the day (1000s of years ago) when people built things themselves, it wasn’t necessary to measure things because everyone did it themselves. I need a bolt as wide as thumb

3. What you talkin’ ‘bout Willis? • However, projects became more complicated, it became necessary to have others work different parts, therefore they had to standardize measurement. moron… Sir, I don’t know what your thumb looks like…

4. Birth of Imperialism • So they decide to take the most popular guy, measure his thumb and call it an inch. This guy was the King! An inch was the width of a thumb A footwas the size of the kings foot, which eventually became 12 inches. A yard was the distance from the tip of a man's nose to the end of his outstretched arm. Eventually, 3 feet became a yard

5. Other systems • The British empire used this method to devise measurements for mass, volume and time. For instance a pound was equal to 7002 troy grains • Other countries developed their own units of measure 7001? That’s stupid! A pound should be 7002… Your sands are no match for our stones! What’s a troy grain? We use wheat seeds

6. Sacre Bleu! C’est tres confusant! • In 1586, the Flemish mathematician Simon Stevin published a small pamphlet called De Thiende ("the tenth"). • He thought counting by decimal fractions would be really nifty! His idea was slow to catch on… I also invented the land yacht! It’s a wagon with sails… WEEEEE!

7. Vive Le France! • Eventually (in the 1800s), the French adopted the Metric System. • In the 1970s many commonwealth (former British colonies) switched to the metric system.

8. SI Units of Measurement • When working with numbers, it is necessary to distinguish between the quantity and its units • Quantity describes something that has magnitude, size or amount (mass, length, etc...) • Units is a quantity adopted as a standard of measurement (kg, m, etc...)

9. The Super SI Seven!

10. GRAMS! • The gram was originally one millionth of the mass of a cubic metre of water • It is currently defined by one thousandth of the mass of a specific Pt/Ir mass that is kept in a vault in France • There are efforts underway to redefine it in terms of physical quantities that could be reproduced in any laboratory with suitable equipment. • The SI unit is kg

11. METRE! • The metre was defined as the length of a particular bar of platinum-iridium alloy • Then it was defined as 1⁄40 000 000 the earth’s circumference • It was then defined as the wavelength of light emitted by a specified atomic transition; • It is now is defined as the distance travelled by light in an absolute vacuum during 1⁄299,792,458of a second

12. SECONDS! • The second was originally1⁄86,400of the mean solar day • It was redefined in 1967 to be 9,192,631,770 periods of vibration of the radiation emitted at a specific wavelength by an atom of caesium-133 • There are plans to redefine it as something which can be reproduced in any equipped lab

13. Temperature! • The Celsius temperature was defined as a scale with 0°C being defined as its freezing point and 100°C being defined as its boiling point at a pressure of one standard atmosphere. • SI unit is the Kelvin (K), a scale whose units have the same "size", but which starts at absolute zero. Zero degrees Celsius equals 273.15 K • NOTE: ° is no longer to be used with Kelvins

14. Moles! • A mole is the amount of a substance which contains as many elementary entities as there are atoms in 12 grams of Carbon-12 • The currently accepted number of atoms in 12 grams of Carbon-12 is 6.02214179×1023 atoms. This number is called Avogadro's Constant

15. Moles! • The relationship of the atomic mass unit (u) Avogadro's number means that a mole can also be defined as: the quantity of a substance whose mass in grams is the same as its formula weight. • For example, Iron (Fe) has a atomic mass of 55.84 u, so a mole of iron has a mass of 55.845 grams. This notation is very commonly used by chemists and physicists.

16. Amperes and Candelas! • An Ampere is a measure of Electrical Currents. We will learn about this later on. • A Candela is a measure of the power emitted by a light source in a particular direction. A common candle emits light with a luminous intensity of roughly one candela.

17. Imperial Systems • Today, the entire world is metric, except for the US, Myanmar and Liberia

18. Zut Alors! • The French tried to implement Metric Time in September 1794. They divided the day into 10 decimal hours. One decimal hour equaled 100 decimal minutes and each decimal minute equaled 100 decimal seconds • It was suspended 6 months later…

19. Counting Metric The great thing about the metric system is that everything is counted by bases of 10!

20. Doing Conversions (when considering Sig Fig)

21. Doing Conversions

22. Doing Conversions

23. Doing Conversions

24. Doing Conversions

25. Word Problem • John is driving 65 km/hr. Simon can run at a speed of 9.2 m/s. Sam rides her bike at a rate of 0.8 km/min. Who is faster? What is the challenge to this problem?

26. Google “convert.exe” www.JoshMadison.com Select “Convert for Windows”